Nonoxidizing heating furnace



' NOV. 1-9, 1929. KELLER 1 ,735,866

NONOXIDIZING HEATING FURNACE Filed May 13. 1926 I I f o /z a o o a o e g e *0 o o o o o G 0/ o o 0 o o o ffZZ/6/ I Gail/L96 166E8 7 Patented Nov. 19:, 1929 GOTITLIEB KELLER, or BRUGG, SWITZERLANQQSSENQR To nemesis-teenage BROWN BOVERI & cm, or BADEN, swIrzEapA m-A JOINT-STOCK COMP-ANY or SWITZERLAND nonoxmrzme nae'rnie ruRNAcE' Application filed May 13, 1926, Serial No. 198,737, at; 'in .Germany aytag-1925. 1

This invention relates to metal working and pertains particularly to apparatus for heat treatment of metal articles on which it a is desired to preserve a surface finish.

provision of apparatus whereby the articles may be heated in the presence of a nonsoxidiz ing gas and loss of the gas prevented.

Another ob'ect is the provision of apparatus whereby the material may be maintained continuously in the presence of the gas during cooling as well as heating.

Still another object is the provision of apparatus whereby the infiltration of air 1s 1 prevented.

A further tus whereby the heat lized.

Other and further ob'ects will be pointed ,0 out or indicated hereina er or will be obvious to one skilled in the art upon an understanding ofthe invention.

In the drawing forming a part of this specification I show one form in which the invention may be embodied, but it is to be understood that the particular construction or arrangement herein shown and described is not to be construed as limiting the claim short. of the true and most comprehensive 80 scope of the invention in the-art.

The drawing is a diagrammatic illustration, in the nature of a sectional elevation of a heating furnace construction with gas relief arrangement.

When finished metal articles, and in particularmetal wire, are to besubjected to heat treatment and it is desired to prevent oxidation taking place, it is customary to fill the furnace with a more or less inert gas, usually object is the provision of apparaof the gas may be uticonnected to a source supplying the gas. This method results in a large consumption of gas and increases the cost of the heat treatment. In addition there is always the danger that The general object of the invention is the carbon dioxide. When the furnace is heatedup, this gas expands and it is therefore neces-' I of during the: cooling-off ,l nod may .be insufficient and allow, airtobe drawn into the muflie, thusv oxidiaingsgthe charge.. Y r

According to the inyention these disadvantages are avoided by connecting anee xpjansion vessel or relief chamber to the furnace,

which I itself is practically gas. tights; This vessel receives the surplus gas driven, out when the furnace is'h'eatedand gives it'up again during the ooling period. There is thus no necessity for the furnace to be permanently connected to the gas supply. Such an arrangement may be very simply realized in practice. The example illustrated by the drawing shows a heat treatment furnace a provided with an electrical heating arrangement 9, the outer casing 0 being made gas tight. The furnace is mounted in a brickwork pit b sunk in the floor, giving a clear ance a 1 round. The cover d which is provided with a liquid seal 7, carries a si hon tube e leading from the interior of the urnace to a point near the bottom of the pit 1;, preferably in a depressiomb which forms atrap or seal against atmos heric air when filled with a heavier gas a ove the end of the tube. A

connection it is provided for supplying a desiredgas to the furnace chamber.

The method of operation is-as follows The articles to be heat treated are introduced into the space a and carbon dioxide is then passed in until the furnace is completely filled; this may be determined by means of a lighted candle. After replacing the cover d the heat treatment is commenced. As a result of expansion due to the heat, a large part' of the carbon dioxide is forced out through the pipe c, is partially cooled in this pipe and thence passes into the pit b where it is completely cooled and collects. [In this way part of the heat in the gas is given up to the furnace, thus increasing the overall economy. On the heat treatment being completed, the charge is allowed to cool, and as the pressure within the furnace falls, the carbon dioxide previously expelled is drawn back into the furnace throu h the tube e, which forms a free inlet fort e gas.- Thus induction of at- I mospheric air is avoided.

' Instead of employing-a pit as an expansion I vessel for the gas, the furnace itself may .be

' disposed in said pit and having such-fit with provided with a double casing, or to ensure still better cooling of the gas it may be led oil into a separate pit. Ifthe charge cannot beallowed to cool down in the furnace itself, I owing to the high rate of production, it may bepacked in" boxes which are placed in the furnace and individually connectedwith the si hon tube leadingto the relief receptacle. en it is-required tocool the charge the boxes are removed from the furnace and com nected by pipes to therelief receptacle.

.What I claim is I In metal treating apparatus 0f the character described, means providing a verticallydisposed pit, a fluid-tight heating receptacle respect thereto as to provide with the same 5 a storage chamber for fluid. and means providlng a passage between said receptacle and said chamber and operating to permit of exchange flow of fluid betweenthe same in either direction.

In testimony whereof I have hereunto-subscrib d my name. at Zurich, Switzerland, on 4 the 8th day of March, A. D. 1926. GO'IITLIEB KELLER. 

